The present invention relates to a heater assembly. More particularly, the present invention relates to an electrothermal heater assembly that is suitable for removing and/or preventing ice accumulation on a gas turbine engine component.
It is desirable to minimize or prevent the formation of ice on certain components of a gas turbine engine in order to avoid problems attributable to ice accumulation. For example, if ice forms on air intake components, the flow of air into the gas turbine engine compressor may become obstructed, which then adversely affects engine operation and efficiency. Furthermore, chunks of ice that break loose from a gas turbine engine component during operation can damage other parts of the engine.
There are many existing methods of removing or preventing the formation of ice on gas turbine engine components. Among these methods is the incorporation (or embedding) of an electrothermal heating element into a gas turbine engine component that is susceptible to ice formation. The heating element may also be applied to a surface of the component. The heating element heats the susceptible areas of the component in order to help prevent ice from forming. The heating element may be a metallic heating element (e.g., a foil element) formed of stainless steel, copper, wire cloth, etc., which typically converts electrical energy into heat energy.
The metallic heating element is typically a part of a heater assembly that also includes a thermally conductive fabric layer attached to and supporting the heating element. For example, the heater assembly may be formed of a metallic heating element embedded into an epoxy fiber reinforced composite structure. In some cases, the fabric layer also electrically insulates an electrically conductive component from the heating element. Typically, multiple plies of fabric are required for sufficient electrical isolation of the metallic heater element.
When the heater assembly is embedded in a composite structure of some gas turbine engine components, the heater assembly replaces some structural elements of the composite in order to maintain the dimensions of the component. In those cases, the heating element accounts for a percentage of the composite structure that forms the component. This may affect the strength and the structural characteristics, such as the transfer of structural loads, of the component. The larger the percentage the heater assembly constitutes, the larger the reduction in composite strength of the gas turbine engine component.
In order to increase the strength of the component that includes the heater assembly, it is desirable to reduce the amount of space the heater assembly takes up in the component. One way of achieving the reduction in space is by reducing the thickness of the heater assembly.